#include<bits/stdc++.h>
using namespace std;
 
#define int long long 
 
#define rep(i,n) for(int i=0;i<(n);i++)
#define pb push_back
#define eb emplace_back
#define all(v) (v).begin(),(v).end()
#define fi first
#define se second
typedef vector<int>vint;
typedef pair<int,int>pint;
typedef vector<pint>vpint;
 
template<typename A,typename B>inline void chmin(A &a,B b){if(a>b)a=b;}
template<typename A,typename B>inline void chmax(A &a,B b){if(a<b)a=b;}
 
template<class A,class B>
ostream& operator<<(ostream& ost,const pair<A,B>&p){
	ost<<"{"<<p.first<<","<<p.second<<"}";
	return ost;
}
 
template<class T>
ostream& operator<<(ostream& ost,const vector<T>&v){
	ost<<"{";
	for(int i=0;i<v.size();i++){
		if(i)ost<<",";
		ost<<v[i];
	}
	ost<<"}";
	return ost;
}

signed main(){
	int N;
	cin>>N;
	vint B(N);
	rep(i,N)cin>>B[i];
	rep(i,N-1)B[i+1]+=B[i];


	int ans=0;
	for(int i=0;i<N-1;i++){
		ans+=abs(i+1-B[i]);
	}
	cout<<ans<<endl;
	return 0;
}